from PyQt5.QtWidgets import QApplication, QMainWindow
from Ui_GUI import Ui_MainWindow
import sys

class MyMainForm(QMainWindow, Ui_MainWindow):
    def __init__(self, parent=None):
        super(MyMainForm, self).__init__(parent)
        self.setupUi(self)

app=QApplication(sys.argv)
win1=MyMainForm()
win1.show()
sys.exit(app.exec_())